Discontinue usage of oslo-rootwrap

Rootwrap should be used from specific console_scripts calling into
oslo.rootwrap.cmd:main, rather than using the specific oslo-rootwrap
wrapper. This matches how nova and cinder now consume oslo.rootwrap,
and ensures a smooth upgrade path.

This change aligns the documentation and shipped files to match how
oslo.rootwrap should be used now.

Change-Id: If01b8840c971d1c6d5c88c7698f5d6a2bf8fd5f0